Many processes are known which produce cheese and cheese-like products using recombining techniques without the release of whey or excess liquid. Products made by such a process are known as fully recombined. A wide variety of concentrated milk proteins are used as ingredients in recombined cheese making. Ultrafiltered milk (retentate), milk protein concentrate (MPC) and retentate powders are ingredients used in the manufacture of cheese and recombined cheese. A feature of the dry ingredients used to prepare fully recombined cheese is that the ingredients can be difficult to incorporate water into and to provide a stable emulsion with fat. Rennet treated milk protein is known to influence the texture of the cheese product and the ability to incorporate fat into the protein-water emulsion.
One of the traditional methods of producing cheese is the use of milk clotting enzymes to produce a gel. Chymosin (rennet) is typically used as the enzyme of choice. The action of rennet on cheese milk is complex. Briefly, proteolytic enzymes such as rennet modify kappa-casein to produce para-kappa-casein. A gel or curd is able to form by heating the enzyme treated milk to temperatures above about 20° C. Enzyme treated milk at almost any practical concentration has suffered from the disadvantage of being difficult to concentrate efficiently without the formation of a gel that impairs the concentration process.
A major technical barrier to solving the enzyme gelation problem during concentration is that to be able to form the desired final product, the gelation property must be able to be finally induced or restored i.e. a way needs to be found that enables the gelation property to be switched off during preparation of the ingredient and then able to be restored as and when required when used in cheesemaking.
It is known to those skilled in the art of cheese making that the properties of the gel formed by the action of enzymes are influenced by the concentration of calcium ions in the milk. Consequently, calcium chloride is a permitted additive in the preparation of natural cheese and is used in circumstances when curd gel strength would otherwise be inadequate.
It is also known that in milk, the calcium is partitioned between a soluble form in the serum phase and an insoluble form (as complex casein phosphate compounds) in the micelles (Singh and Fox, 1987). Equilibrium exists between the two. Ultrafiltration combined with diafiltration is able to remove significant amounts of soluble calcium from milk. Methods are known to enhance the removal of soluble calcium during membrane concentration by the acidification of the milk or retentate prior to, or during treatment, or by the addition of salt, or by the addition of calcium chelating agents such as citrate (Bastian, Collinge and Ernstrom, 1991). There is a practical and economic limit to the use of these agents if the requirement is to fully suppress gelation upon the addition of rennet. The value, or the disposal cost, of the diafiltration permeate becomes increasingly uneconomic as the extent of diafiltration increases, and especially when contaminated with agents that are added to promote the removal of calcium.
It is known that when solutions of sodium caseinate are treated with rennet, no gel forms. However, a gel is able to be formed upon the addition of calcium and the application of heat (Varnam & Sutherland, 1994). Treatment of skim milk with a calcium sequestering agent such as citrate or EDTA sufficient to remove at least 33% of the colloidal calcium phosphate removes the ability of rennet to cause the skim milk to form a gel. However, a gel can be subsequently induced by the incorporation of calcium salts (Udabage, McKinnon and Augustin, 2001).
Poarch (U.S. Pat. No. 4,202,907) discloses a process that takes advantage of these phenomena. The means to suppress gel formation in renneted milk protein solutions is achieved by the removal of calcium. Incorporation of calcium at some later stage restores the gelation characteristic of the rennet treated milk protein. Poarch produced a renneted sodium caseinate that was dried without gelation as an ingredient for subsequent use. The ingredient was mixed with water, a soluble calcium salt and comminuted meat (sausage batter). Upon heating, a gel formed that retains fat and moisture in sausages and other formed meat products during the cooking process.
It would be desirable to form a dried cheese ingredient which does not gel after the addition of a milk clotting enzyme, which is capable of being dried efficiently and which can be reconstituted to form a gel by the addition of water with heating, with or without adding calcium ions.
It is an object of this invention to go someway towards achieving this desideratum or at least to offer the public a useful choice.